Test naming conventions in PyTest - Test Execution Trace

Test Overview

This test checks that a simple function returns the correct result and uses proper test naming conventions in pytest. It verifies that the test function name starts with test_ so pytest can discover and run it.

Test Code - pytest

PyTest

import pytest

def add(a, b):
    return a + b

def test_add_two_numbers():
    result = add(2, 3)
    assert result == 5

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Test runner starts and discovers test functions starting with 'test_'	pytest collects test_add_two_numbers from the test file	—	PASS
2	pytest runs test_add_two_numbers function	Inside test_add_two_numbers, calls add(2, 3)	—	PASS
3	Assert that result equals 5	result is 5 from add function	assert result == 5	PASS
4	Test completes successfully	pytest reports test_add_two_numbers PASSED	—	PASS

Failure Scenario

Failing Condition: Test function is not named starting with 'test_' so pytest does not run it

Execution Trace Quiz - 3 Questions

Why must pytest test functions start with 'test_'?

A So pytest can find and run them automatically

B To make the test run faster

C To avoid syntax errors

D To make tests run in parallel

Key Result

Always name your test functions starting with 'test_' in pytest so the test runner can find and execute them automatically.

Practice

1. Which of the following is the correct way to name a test function in pytest so it is automatically discovered?

easy

A. test_login_functionality

B. check_login_functionality

C. LoginTest

D. verifyLogin

Solution

1. Step 1: Understand pytest test discovery rules

   pytest automatically finds test functions that start with test_.

2. Step 2: Check each option against the rule

   Only test_login_functionality starts with test_, so pytest will find it automatically.

3. Final Answer:

   test_login_functionality -> Option A

4. Quick Check:

   Test names start with test_ = C [OK]

Hint: Test names must start with test_ to be found [OK]

Common Mistakes:

• Not starting test names with test_
• Using camelCase instead of snake_case
• Using class names instead of functions

2. Which of the following test function names is syntactically correct in pytest?

easy

A. test-user-login

B. test-UserLogin

C. test_user_login

D. test user login

Solution

1. Step 1: Identify valid Python function names

   Function names must use letters, numbers, and underscores only; no spaces or hyphens.

2. Step 2: Check each option

   test_user_login uses underscores and is valid; others use hyphens, spaces which are invalid.

3. Final Answer:

   test_user_login -> Option C

4. Quick Check:

   Underscores allowed in function names = D [OK]

Hint: Use underscores, no spaces or hyphens in test names [OK]

Common Mistakes:

• Using hyphens in function names
• Including spaces in test names
• Using camelCase instead of snake_case

3. Given the following pytest code, which test functions will pytest discover and run?

def test_addition():
    assert 1 + 1 == 2

def check_subtraction():
    assert 2 - 1 == 1

def testMultiplication():
    assert 2 * 3 == 6

class TestDivision:
    def test_divide(self):
        assert 6 / 2 == 3

medium

A. test_addition and test_divide only

B. All four functions

C. test_addition, testMultiplication, and test_divide

D. test_addition only

Solution

1. Step 1: Identify pytest discovery rules for functions and methods

   pytest finds functions starting with test_ and methods inside classes named Test* starting with test_.

2. Step 2: Analyze each function/method

   test_addition is found; check_subtraction is ignored; testMultiplication is ignored due to camelCase; test_divide inside TestDivision class is found.

3. Final Answer:

   test_addition and test_divide only -> Option A

4. Quick Check:

   Functions/methods start with test_ = A [OK]

Hint: pytest finds test_ functions and test_ methods in Test* classes [OK]

Common Mistakes:

• Assuming camelCase test names are found
• Ignoring test methods inside Test classes
• Thinking all functions are discovered

4. You wrote a test function named Test_login but pytest does not run it. What is the most likely reason?

medium

A. Function is inside a class without Test prefix

B. Function name contains uppercase letters

C. Function is missing parentheses

D. Function name does not start with lowercase test_

Solution

1. Step 1: Recall pytest naming rules for functions

   pytest requires test functions to start with lowercase test_ exactly.

2. Step 2: Analyze the function name Test_login

   It starts with uppercase T, so pytest ignores it.

3. Final Answer:

   Function name does not start with lowercase test_ -> Option D

4. Quick Check:

   Lowercase test_ prefix required = A [OK]

Hint: Test function names must start with lowercase test_ [OK]

Common Mistakes:

• Using uppercase T in test function names
• Assuming pytest finds any function with 'test' inside
• Ignoring function naming case sensitivity

5. You want to write clear pytest test names that describe what they check. Which of the following is the best test function name for checking if a user can log in with valid credentials?

hard

A. test1

B. test_valid_user_login

C. test_login

D. test_user_login_with_valid_credentials_and_session_creation

Solution

1. Step 1: Consider clarity and brevity in test names

   Good test names are clear but not overly long or vague.

2. Step 2: Evaluate each option

   test_valid_user_login clearly states the test purpose concisely. test1 is vague. test_login is too general. test_user_login_with_valid_credentials_and_session_creation is too long and hard to read.

3. Final Answer:

   test_valid_user_login -> Option B

4. Quick Check:

   Clear and concise descriptive names = B [OK]

Hint: Choose clear, concise test names describing the check [OK]

Common Mistakes:

• Using vague or generic names like test1
• Writing overly long test names
• Using names that don't describe the test purpose